michel123456

I have serious doubts. I think we are overestimating our knowledge. "Why" is a silly question when you cannot answer it, and a very interesting one when you can.

Darkness is a phenomena, it is not something that properly "exist". At any point of the universe, you can receive light: light is everywhere. And a whole bunch of other radiations. You cannot go in some place and suddenly not observe the stars around you (except closed in some box together with a cat, or closing your eyes). The Universe is an ocean of light. The fact is that the only light we can perceive is that one who enter our eyes. We cannot see the vast majority of light that pass over our heads. That's what we call darkness. So, darkness is not absence of light, darkness is anything that we cannot observe.

In this diagram, the twin travel is represented with the blue trajectory O-B-A. As far I can see, all mathematical analysis of the twin travel represents the trajectory O-B-C. There is no mathematical account of the U-turn in point B. Everything is calculated as if the twin traveled twice the distance d, that is 2d, which is the path length*, no matter of what happened at point B. In fact the path is correct, but displacement is null. IMHO there is an obvious physical difference between A and C: they have different spacetime coordinates. The conclusion we usually extract from calculations is those that would happen if A and C were in contact. But they are not. If you prefer, there should be a difference between the equations describing an object getting away and the equations describing an object approaching. *as observed from A.

I asked for a number. Units are yours.

That's the point. You should expand on that. What is invariant version of the Earth-Sun distance on which everyone can agree?

I don't think it is to protect from frost or to reduce heat loss. Frost can happen at night as well, and temperature loss can happen anytime. IMHO the "clear morning" indicates that at this particular moment radiation from sunrise can burn, or at least produce a thermal shock.

In the Minkowski diagram article in wikipedia, under the paragraph Time dilation, here below the following graph: Quoted from wiki: and the beginning of the explanation: Emphasis mine. My question is the following: Can A observe B? I think not, because light travels at C, which is a diagonal not represented on this graph. IMHO what A is observing is the point B2 in the following graph: Point B is simultanate but it is not observable.

Interesting comment. 1. The " that travel slower than the speed of light.' is unnecessary. Time begins when there exist matter. I agree 100%. It should be a hint (Big Ben sized) on the nature of mass & gravity. 2. People here know my position on this. I suppose the OP question should be then "how to create pure energy?".

a spring a torsion spring. A catapult.

Oh, that was the connected. I ment something different. Contrarily to intuition, something that is on metre away from you and in your present, is not causally connected to you. Because time is needed for any interaction to happen, bodies in mutual present are not causally connected. So what I say is that one metre is pretty close for something "disconnected", there is no need to look at far away galaxies.

...and the dimension of the twin himself & his clock who were contracted during the travel. Till this point we agree (what a relief!0 There I am confused I'll try to explain: Planet A "at rest", spaceship B at Cap canaveral. B is at rest. 9,8,7,6,5,4,3,2,1,... psit, B is propulsed into space: acceleration. B travels for a period of time T1 as observed from A (for time T2 as observed from B) till the middle of the travel. At this point, B operates a U-turn and comes back. When she makes the U-turn, B is in the same FOR with A. I mean, at that moment, relative velocity between A & B is null. Otherwise, it is not a U-turn. (the same goes for an orbit) Thus, at this moment, time dilation & length contraction have vanished, as observed by A. (they never existed as observed by B on herself) The first part of the travel consisted of acceleration & deceleration ,as observed by A. The come-back travel will consist of acceleration & deceleration as observed by B and smooth landing at Cap Canaveral as observed by both. As seen from A, the travel consisted of 4 parts: 1. acceleration away 2. deceleration away 3. acceleration back 4. deceleration back. As seen from B the travel consisted of: 5. acceleration away 6. deceleration away 7. acceleration back 8. deceleration back. Measurements 1 from 8 will be different for both observers. But I think that measurements 7 & 8 cancel out measurements 1 & 2 (they are exactly symmetric) and that 5 & 6 cancel out 3 & 4, so that both observers will agree at last on everything.

I already standed corrected by Swansont who answered immediately: I never spoke about tan, one could use cotangent instead, but you are right. In my original sketch, rods were vertical & time was going horizontaly from left to right (like a comic strip). When I putted time vertical to make it look like a conventional space-time diagram, I forgot to switch the indication of the angle. You may notice that the angle is not 45 degrees, that is intentionally because as you wrote the time axis is not ct as in a Minkowski diagram. But it is still a space-time diagram. A very simple one, elementary one could say. I don't understand the reason why to call it an "artificial" one.

So time changed from a maximum dilated value to a less dilated value: time contracted. Or do we have a language issue here?

When relative speed diminishes, you must agree that time dilation diminishes too. I hope.

When you look at a simple Minkowski diagram, you may notice that there are regions of spacetime that are causally diconnected from us while very close. The left & right part of the diagram are evident examples.

Then, how do you account for this comment: (emphasis mine) How does it "go away"? I have understood that when the 2 clocks come back together, we all agree that their frequency will be the same again. How is it possible to obtain such a result accounting only on time dilation? There seems to be some inconsistency.

That's what I say, it is asymmetric. And I am not comfortable with the idea. --------------------------------- edited. And what about length contraction?

Rigney. When I engage conversation with someone, I always begin full of respect, mainly because I don't know the other person. Sometimes, respect diminishes. Sometimes not. You belong to the second category.

Why persistent? In order to re-unite the two clocks, don't you measure a negative acceleration (deceleration) exactly the same as the original acceleration? Why the one counts (when the 2 clocks get away from each other) and the other don't (when they get together). There is something terribly asymmetric in this situation.

_Pose is suppose without sup. _I am in a deep trouble since it is a profound mistake. _I agree there is a conceptional issue when equalizing [math] X [/math] with [math] S [/math]: [math] S [/math] is zero, and in the diagram [math] X [/math] is obviously not null. _Trivial is the answer I first thought would appear, that is C=1.

You can call me Michel. 123456 is a code. Yes. But I am not so passionate in your device as you are, and I didn't go into a very profound cogitation. Basically, my argumentation ends with the "maybe this" comment.

I thought the electron was something like a cloud.

What's happening here? Senility! (I had the impression that most people on this forum was very (very) young). What are you doing? No no no, you have to fight till the end, never give up, especially when you realize you were wrong. Never admit a defeat. And you, John, you must laugh and ridiculize your adversary. Beat him to death.That's the way it should go.

(emphasis & bold numbers mine) (1)Aryan (2)untermensch Bad memories.

(emphasis mine) FMI Do you have some source?